The present invention relates in general to time locks for bank vaults and safes and similar timed high security devices for security receptacles, and more particularly to manually settable time locks provided with means for releasably holding its bolt controlling plunger against premature release from external shocks or vibrational movement imparted to the time lock, and wherein the time lock includes means which releases the plunger for unlocking movement when the timing mechanism times down to zero.
Heretofore, time locks have been in common, widespread use to place bank vaults and similar safes, security spaces, and the like in a lockout condition rendering them disabled from being opened in the normal way by bank personnel, as by proper dialing of a combination lock, during certain chosen times, such as between the bank closing time one day and its opening time the next banking day. In recent years, these time locks have customarily involved a box or case having two or three timer units or clockwork movements, to provide backup redundancy in case one or two of the timer units fail, each of which has a settable dial graduated in hours and set from a key insertable into openings in the time lock case to indicate the desired locking hours or time lapse between setting of the timer and the time of opening of the vault the next working day. Each timer unit or movement customarily has a main spring and gear system to concurrently wind the main drive spring for the clockwork mechanism and drive the dial in a windup or increasing time lapse direction relative to a stationary pointer or index mark, and the dial usually has a trip pin or stub fixed on the dial face to engage an abutment surface on the end of one of a plurality of rigid arms extending from a transversely movable carrier when the associated timer unit dial times out to zero time and moves the carrier to a release position allowing a snubber bar connected in the usual manner to the bolts for the vault door, as by connection to a common control bar for the bolts to retract to unlocking position. U.S. Pat. No. 4,062,210 granted Dec. 13, 1977 to the assignee of the present invention discloses a time lock of this general type.
Alternatively, a snap action trip arm mechanism may be provided with each timer unit to abruptly kick the carrier toward release position at zero time, as disclosed in U.S. patent application Ser. No. 940,834 filed Sept. 7, 1978 by Charles G. Bechtiger et al, owned by the assignee of the present application. The carrier typically has three of such rigid arms extending to abutment ends located at the zero time positions for the trip pins of each of the three dials of the three timer units, so that any one of the three trip pins when it engages the abutment end surface of the associated extension arm of the carrier will push the carrier toward its release position by the force of the stored energy in the associated main drive spring to unlock the time lock.
The carrier is usually only spring biased to locking position and typically moves only a short distance transversely of the time lock to effect release of the time lock, usually by withdrawing a small abutment surface bounding a slot from holding position relative to a notch or shoulder of a push lever or actuator accessible from the front of the time lock case and allowing a blocking member to drop from blocking relation to a snubber bar connected to the vault door bolts. It is possible that vibration of the time lock mechanism from various sources could cause sufficient movement of the carrier toward release position against the spring bias of the usual carrier retaining spring to effect accidental or surreptitious release of the time lock. Sidewise accelerations issuing for instance from external shocks can exert a force onto the carrier plate in the direction of making it open the lock. A force acting in a direction toward the release position of the carrier may overcome the retaining action of the carrier retaining spring. The main carrier plate in that type of prior art time locks must be strong and therefore massive because of functional requirements. The retaining spring cannot be made very strong in order not to overload the timing mechanisms when releasing. The ratio of carrier mass to retaining spring force is therefore high and cannot be reduced below a limit given by consideration of design and proper functioning. Therefore, there exists always a force of relatively small value sufficient to shift the carrier plate in the opening direction.
More specifically, the spring loaded carrier, for example as indicated at reference character 60 in said earlier U.S. Pat. No. 4,062,210, which is designed to be shifted to the unlocking or plunger release position when the dial pin or kicker arm of any one of two or three independently working time movements or timer units engage and shift the carrier, represents a heavy mass which can slide freely in the release direction, hindered only by the force of its biasing spring. Shocks severe enough and in the proper direction lead to accelerations of the carrier high enough to overcome this spring force, and thus release the plunger. Furthermore, high or severe shocks, applied in other directions than the direction of release movement of the carrier, create vibrations within the time lock structure because the components of the time lock structure are normally not rigid enough. Especially, the timing mechanisms or movements mounted on the base plate represent a very high mass which causes the base to bend for several millimeters. Instances have been observed where, after sever shocking, the apparently solid base structure of the time lock is permanently bent by as much as 5.degree. to 10.degree.. This implies that during a very short time, the timing mechanisms or movements, and with them, of course, their dials and release pins on the dials, undergo controllable movements relative to the base structure onto which the carrier is mounted. If shocks occur in the last thirty to sixty minutes before normal release time, the release pins on the dials, which are already very close to the carrier, may push forward because of the generated oscillations to the carrier, releasing the plunger prematurely. The concurrence of the conditions of severe shocks and short time settings has been many times observed in certain types of shock tests conducted by some authorities whose approval is required for certain types of time lock installations.
An object of the present invention is the provision of a novel mechanism for controlling latching and release of the plunger of time locks designed to overcome the above described problem, by providing a plunger latching structure which will oppose by a sufficiently high counterforce the dynamic opening forces resulting from relative movements between the timing unit release pins and the locking system during shocks, but which will not oppose by any additional counterforce the normal opening forces from the release pin during normal operation in the absence of shocks.
Another object of the present invention is the provision of a novel time lock mechanism described in the immediately preceding paragraph, wherein the high counterforces opposing the dynamic opening forces are produced in a relatively inexpensive way by introducing a gear train between the locking device and a relatively small mass to increase the virtual inertia of the system, introducing what appears to be a very high mass at the input of the locking device, and providing an elastic link between the input and the mass enabling the system to absorb movements at the input generated by severe shocks without the output moving correspondingly, the output being held back dynamically by its large virtual inertia.
Another object of the present invention is the provision of a time lock as described in the immediately preceding paragraph, wherein eccentric linking is provided between components of the latching and release mechanism enabling setting up for zero time in a quick and effective manner.
Another object of the present invention is the provision of a novel latching and releasing mechanism for the plunger of a time lock having plural time movements or timer units, wherein a base plate for the mechanism is fixed onto the base of the time lock in a non-sliding mounted relation to assure higher stability and improved precision.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.